The objective of this proposal is to describe the cellular and molecular events initiated by the binding of gastrin to its receptor on the parietal cell. This study will involve the use of isolated parietal cells and also a functional preparation of parietal cells in culture. We have currently applied previous techniques of 125I-gastrin binding and 14C-aminopyrine accumulation for characterizing gastrin receptor-function studies in isolated cells; and have also applied current techniques of electrophysiological analysis of cultures, to the study the effects of gastrin on PD, resistance, and H+ secretion of parietal cell monolayer cultures. Both electrophysiological and other biochemical measurements, such as 45Ca2+ flux studies, will be correlated to establish a temporal and kinetic relationship between gastrin binding and the sequence of events leading up to the activation of the H+ pump. The specific aims of this study are: 1) To initially characterize the binding properties of the gastrin receptor on isolated cells and in culture. 2) To define the role of calcium in gastrin regulation of parietal cell electrophysiology, morphology and H+ secretion. 3) To further characterize potentiating interactions of other agonists with gastrin on isolated cell 14C-aminopyrine accumulation and parietal cell culture electrophysiology and morphology. 4) To establish an optimum short-term primary cu.ture system for the overall study of gastrin action; thus, the ability of gastrin to also maintain differentiation of these parietal cell cultures will be analyzed using light, transmission and scanning electron microscopy and histochemistry.